It’s all about capacity, and the numbers are the numbers.
I’m not sure why I decided to ignore the specs on the Shimano RD 6700 Ultegra rear derailleur as they were pretty clear: 39T capacity w/28T max sprocket. But, no, I bought into several accounts of using this derailleur on 34t cassettes, etc. and rolled the dice.
Yeah, well… Once it was installed it was pretty clear that the cage just wasn’t long enough to support the 44T difference on our Calfee or the 32T rear sprocket. It was close, very close, but close doesn’t cut it when your derailleur’s upper idler pulley is making contact with the 32t sprocket teeth in the ‘alpine gear’ with the B-screw all the way out.
Thankfully, the Ultegra 6700 10-speed shifters and 10-speed cassette work just fine with my late 1990’s vintage Shimano XTR / RD-M950 8 speed derailleur. No, its specs also come up a little short on capacity, but since it supports a 32T rear sprocket it keeps the idler pulley and 32t rear sprocket separated. Oh, and even though it was designed for an 8 speed system, the derailleur geometry seems to work just fine with the 10 speed cassette spacing and Shimano Ultegra 6700 shifters, in the stand and on the road.
So, the Ultegra is headed back to the wonderful eBay seller who had made it available to us for a refund and we’ll just use the vintage XTR M950 rear derailleur until any problems develop.
Looking forward to getting some tandem time this coming weekend as we’ll be off the pedal bikes for the next two weekends, perhaps even the next three.